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This Week in PNAS: May 7, 2013

A University of California-led team sequenced the genomes of dozens of Batrachochytrium dendrobatidis isolates in an effort to understand the evolutionary history of the fungus — an amphibian pathogen that's had particularly detrimental effects on amphibian populations in the Americas. As they report in the early, online edition of the Proceedings of the National Academy of Sciences, the researchers found a great deal of genetic diversity amongst 29 B. dendrobatidis isolates collected from sites around the world, consistent with a complex evolutionary history for the fungus. They also saw signs of selective pressure on genes coding for protease enzymes, suggesting these processes are prone to shifts during evolutionary transitions.

Mutations to the RASA1 gene can cause conditions involving abnormalities to the lymphatic fluid-carrying vasculature, according to a study by researchers from Texas and Michigan. The group unearthed frame-shift mutations in RASA1 when they did whole-exome sequencing on a 20-year-old individual with a lymphatic condition called Parkes-Weber syndrome and his unaffected parents. Together with analyses of the affected individual's vasculature, the findings suggest RASA1 mutations may lead to unusual lymphatic vascular architecture, study authors say — a notion supported by experiments in mice missing the RASA1 gene. Even so, RASA1 mutations seem to have variable expressivity since the unaffected father in the exome-sequenced trio carried the same RASA1 alteration found in his Parkes-Weber syndrome-affected son.

For another study slated to appear online this week in PNAS, Cornell University researchers relied on data from the Drosophila Genetic Reference Panel to tally up natural genetic variation in the fruit fly — information that they used to help find new players in endoplasmic reticulum stress response pathways. The team treated flies from 114 sequenced DGRP lines with an ER stress-inducing compound called tunicamycin. By following flies' survival times and looking at how they corresponded with both array-based gene expression profiles and SNP patterns, the investigators identified 25 candidate ER stress response genes. Their follow-up functional experiments suggested that at least 17 of the genes could be plausible ER stress response pathway participants.